In response to increasing environmental regulations of underground storage and pipe delivery systems of hazardous liquids such as, motor fuels environmental regulators have been seeking safer and more reliable tank, piping and sump containment systems. In 1988 the US Congress passed the “Clean Water Act” that contained legislation that mandated that fuel handling facilities, like service stations insure that the fuel that was stored in underground storage tanks (UST's) and supplied via underground piping to the fuel dispensers could not leak into the environment.
As a result of this federal legislation and other state laws governing the environmental safety of UST's and their associated piping systems, manufacturers introduced a variety of double-wall tank and piping systems and electronic leak detection systems.
In the 1960's non-metallic fiberglass tanks and piping was introduced to replace unprotected steel tanks and piping that would corrode over time. In the 1980's double-wall tanks and piping with leak detection were introduced to the market for added protection. In the 1990's double-wall flexible underground piping systems were introduced in an effort to minimize the number of piping joints and pipe cracking within a pipe distribution system.
The major difference between flexible and rigid underground piping systems was whether the flexible piping was available on a long continuous roll or reel. Rigid steel or fiberglass piping was available in bundles of straight lengths. Used in conjunction with “tank sumps” located on top of the tanks and “dispenser sumps” located under the dispensers, all flexible piping joints could be secondarily contained within these sumps. Because flexible piping can turn corners and comes in long continuous lengths it does not require pipe-to-pipe connectors or directional fittings in order to route the piping from one containment sump to another.
Manufacturers of flexible piping systems boast that their piping systems have all piping joints contained inside a secondary containment sump located either on top of the tank or under each fuel dispenser. This is important because over 90% of piping leaks occur at the piping joints and with flexible piping systems all piping joints can be inspected and accessed from above ground without the need for excavation. Another significant advantage of flexible piping systems is that they can be installed inside a larger chase (duct or conduit) that allows a flexible pipe section to be removed and replaced without the need for excavation. These flexible piping systems would be similar to my U.S. Pat. Nos. 4,971,477, 5,263,794, 5,297,896 and 5,527,130.
Over the years there have been significant improvements in underground double-wall UST's and piping systems due to increasing environmental regulations and tighter testing standards, such as UL, SEN and Kiwa testing standards. One component of underground fuel storage and delivery systems that is currently under investigation for improved design are under-dispenser containers, called “dispenser sumps” and pump containment sumps, called “tank sumps”.
Containment sumps installed today are typically large hollow containers made of either rotationally molded polyethylene or fiberglass. Tank sumps are typically large enough (36″ to 48″ in diameter) to allow installers sufficient room to install the dispensing pumps and various types of plumbing assemblies and piping connections within them. These tank sumps would be similar to those described in my U.S. Pat. D309,308. Dispenser sumps on the other hand are deep containers with a narrow top opening that makes access difficult for installing a multitude of primary and secondary piping plumbing connections and riser assemblies. The limited access into such deep containers (30″ to 48″ deep) makes installation and future repair very difficult and time consuming. These deep dispenser sumps would be similar to those dispenser sumps described in my U.S. Pat. Nos. 4,971,477, 5,263,794, 5,297,896 and 5,527,130.
Prior to these deep dispenser sumps there existed shallow dispenser pans. The problems associated with these dispenser pans was that not all plumbing connections could be contained within this shallow container. This primary drawback led to the virtual extinction of shallow dispenser pans by the middle of the 1990's. The difference in terminology (“pan” vs. “sump”) is that not all of the piping connections are contained within a dispenser pan whereas they are in a dispenser sump.
There are a number of other problems associated with deep, flat, vertical sided containers like that of today's dispenser sumps, besides limited accessibility. Conventional dispenser sumps are sufficiently deep enough to allow the piping to enter the container through the vertical sidewall horizontally. The piping makes connection inside the sump with either a tee or elbow fitting and is routed upward to a shear valve by means of a steel riser pipe or flexible connector. Dispenser sumps also require large flat sidewalls to effectively install a multitude of pipe entry seals at different elevations. The combination of a deep container having large flat side walls can have problem with concaving (bowing inward or outward), collapse, or cracking due to ground pressures caused by high ground water conditions and/or being installed in fluid backfill materials like sand.
Leaking pipe entry seals, deformed and cracked sidewalls have led some state environmental regulators to consider and/or mandate monitored double-wall containment sumps and their associated pipe entries.
It is the significant depth of these conventional deep dispenser sumps that causes so many problems. The concaving of the large flat sidewalls can damage pipe entry seals, cause cracks in the sump container wall or even cause damage to the fuel delivery piping contained within. To repair any damage to these sumps is very difficult and time consuming because of the limited access. These deep dispenser sumps can also contain a large volume of leaking fuel before the leaks are detected that could cause a significant safety and environmental risk.